Interstellar scattering, the North Polar Spur, and a possible new class of compact galactic radio sources

1979 ◽  
Vol 228 ◽  
pp. 755 ◽  
Author(s):  
J. J. Rickard ◽  
W. M. Cronyn
Keyword(s):  
Radio Sources ◽  
New Class ◽  
The North ◽  
Interstellar Scattering ◽  
North Polar ◽  
Galactic Radio

Chinese Historiography in the Age of Maturity, 960–1368

2018 ◽  
Author(s):  
Charles Hartman
Keyword(s):  
South China ◽  
Song Dynasty ◽  
Political Power ◽  
Examination System ◽  
Economic Expansion ◽  
New Class ◽  
The Song Dynasty ◽  
The North ◽  
System A ◽  
Age Of Maturity

This chapter looks at how the Song dynasty (960–1279) reconsolidated central power and eliminated the provincial regimes that had developed in the wake of Tang decentralization. During the first thirty years after 960, they fostered astute policies that promoted and took advantage of continuing economic expansion. To administer their new polity, the Song emperors recruited through the examination system a new class of bureaucratic elite that Western writings on China often call the ‘literati’. The aristocrats of Tang had given way to the merchants and bureaucrats of Song. However, although the Song expanded Chinese economic and political power into South China, it never completed the conquest of all the traditional Chinese lands in the north. The Song coexisted with a series of alien or conquest dynasties to its north and west.

scholarly journals Avalanches of the martian north polar cap

2020 ◽  
Author(s):  
Patricio Becerra ◽  
Susan Conway ◽  
Nicholas Thomas ◽  
Keyword(s):  
Polar Regions ◽  
Martian Surface ◽  
Polar Cap ◽  
Water Ice ◽  
The North ◽  
Imaging Science ◽  
Resolution Imaging ◽  
North Polar ◽  
Gas Expansion ◽  
Trigger Mechanisms

<p>In 2008, the High Resolution Imaging Science Experiment (HiRISE) on board NASA’s MRO fortuitously captured several discrete clouds of material in the process of cascading down a steep scarp of the water-ice-rich north polar layered deposits (NPLD). The events were only seen during a period of ~4 weeks, near the onset of martian northern spring in 2008, when the seasonal cover of CO2 is beginning to sublimate from the north polar regions. Russell et al. [1] analyzed the morphology of the clouds, inferring that the particles involved were mechanically analogous to terrestrial “dry, loose snow or dust”, so that the events were similar to terrestrial “powder avalanches” [2]. HiRISE confirmed the seasonality of avalanche occurrence the following spring, and continued to capture between 30 and 50 avalanches per season (fig. 1b,c) between 2008 and 2019, for a total of 7 Mars Years (MY29–MY35) of continuous scarp monitoring.</p><p>In this work we will present statistics on these events, in an attempt to quantify their effect on the mass balance of the NPLD, and with respect to competing processes such as viscous deformation and stress-induced block falls that do not trigger avalanches [3,4]. We also use a 1D thermal model [5] to investigate the sources and trigger mechanisms of these events. The model tracks the accumulation and ablation of seasonal CO2 frost on a martian surface. Russell et al. [1] support an initiation through gas-expansion related to the presence of CO2 frost on the scarp. Therefore the amount of frost that lingers on different sections of the model scarp at the observed time of the avalanches will provide evidence either for or against this particular mechanism. We will present preliminary results and discuss their implications.</p><p>References: [1] P. Russell et al. (2008) Geophys. Res. Lett. 35, L23204. [2] D. McClung, P.A. Schaerer (2006), Mountaineers, Seattle Wash. [3] Sori, M. M., et al., Geophys. Res. Lett., 43. [4] Byrne et al. (2016), 6th Int. Conf. Mars Polar Sci. Exploration [4] C. M. Dundas and S. Byrne (2010) Icarus 206, 716.</p>

scholarly journals Widespread Megaripple Activity Across the North Polar Ergs of Mars

2021 ◽  
Author(s):  
Matthew Chojnacki ◽  
David A. Vaz ◽  
Simone Silvestro ◽  
David C.A. Silva
Keyword(s):  
The North ◽  
North Polar

scholarly journals A Catalogue of Galactic Radio Sources

1968 ◽  
Vol 21 (3) ◽  
pp. 369 ◽  
Author(s):  
MJL Kesteven
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Galactic Plane ◽  
Radio Sources ◽  
Galactic Radio

The results of a survey of radio sources in the galactic plane in the longitude range 1800 to 400 with the 1 mile Molonglo Cross telescope at 408 MHz are presented. The methods of observation and reduction are described briefly. The catalogue lists the position, flux density, size, and spectral index for 80 sources

scholarly journals Some Observations of Shell-type Galactic Radio Sources

1967 ◽  
Vol 20 (3) ◽  
pp. 297 ◽  
Author(s):  
ER Hill
Keyword(s):  
Radio Emission ◽  
Spherical Symmetry ◽  
Supernova Remnants ◽  
Supernova Remnant ◽  
Milky Way ◽  
Radio Sources ◽  
Radio Observations ◽  
Shell Type ◽  
Rosette Nebula ◽  
Galactic Radio

Radio evidence for two new supernova remnants in the Southern Milky Way is presented. Some new observations of the known supernova remnant, source 1439-62, and of the Rosette nebula, a shell source but not a supernova remnant, are also presented. The problem of finding model shells to fit the radio observations is considered and it is shown that the radio emission from 1439-62 is unlikely to originate in a shell with spherical symmetry.

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